1. Technical Field
The present invention relates to A/D converter circuits, electronic apparatuses, and A/D conversion methods.
2. Related Art
As an A/D converter circuit that converts an analog signal to digital data, a successive approximation A/D converter circuit is known. The successive approximation A/D converter circuit is typically equipped with a comparison circuit, a successive approximation register, and a D/A converter circuit, and performs analog-to-digital conversion of a sampled signal (a sampled and held signal) of an input signal by the successive approximation operation to thereby output digital data. As one of the common implementations of the successive approximation A/D converter circuit, the technology described in Japanese Laid-open Patent Application HEI 08-321779 (Patent Document 1) is known.
The conversion accuracy of such an A/D converter circuit mostly depends on the accuracy of the D/A converter circuit. When increasing the accuracy of the D/A converter circuit, the area of the capacitors (in the case of a charge-redistribution type) or the area of the resistances (in the case of a ladder resistance type) may be increased. This causes the circuit to become larger in scale. On the other hand, in order to suppress an increase in the circuit scale, some measures may be added to the circuit of the D/A converter circuit. However, this may lead to problems, such as, generation of missing codes, due to errors of differential nonlinearity (DNL), integral nonlinearity (INL) and the like.
The A/D conversion characteristic such as DNL and INL may be improved, but such improvement may reduce the dynamic range in A/D conversion. This is not desirable for the performance required for A/D conversion.